Loading…
TQFP-44 · ATMEGA32U4-AU
Active8-bit AVR MCU with USB
ATMEGA32U4-AU
Microchip Technology · TQFP-44 · 8-bit AVR MCU with USB
Price on Request
Get a competitive quote within 24 hours. Volume discounts available. Shenzhen stock ships in 1-2 business days.
Overview
The ATMEGA32U4-AU is the AVR that put native USB inside an 8-bit microcontroller: it integrates a USB 2.0 full-speed and low-speed device controller with endpoint 0 plus six programmable endpoints, so it enumerates as a keyboard, mouse, mass-storage, CDC serial or composite device with no external bridge chip. That is why it is the silicon in the Arduino Leonardo, Arduino Micro, SparkFun Pro Micro and the overwhelming majority of custom QMK mechanical keyboard controllers. In the 44-lead TQFP (-AU suffix) it exposes 26 programmable I/O lines with 32 KB Flash, 2.5 KB SRAM and 1 KB EEPROM.
Speed and supply need care. The device operates from 2.7 V to 5.5 V, but the maximum frequency is 8 MHz at 2.7 V and 16 MHz at 4.5 V; USB full-speed timing additionally requires a 16 MHz clock, so 3.3 V boards must run at 8 MHz with the USB PLL configuration adjusted. Beyond USB the part is a capable AVR: a 12-channel 10-bit ADC with differential inputs and programmable gain, a USART with hardware flow control, master/slave SPI, a 2-wire interface, four timer/counters including a high-speed timer with its own 64 MHz PLL for high-resolution PWM, an analog comparator, on-chip temperature sensor, JTAG with debug, watchdog and six sleep modes.
For sourcing, Microchip lists the ATmega32U4 as Active, and demand is sustained by keyboard and HID manufacturers, so the TQFP-44 and QFN-44 (-MU) both stay in circulation. Counterfeit risk here has a distinct signature: remarked ATmega16U4 dies sold as 32U4 (half the flash, signature bytes 1E 94 0x88 family versus 1E 95 87 for a genuine 32U4), and cheap clones whose USB endpoint memory fails under composite descriptors. Always read the signature bytes and test USB enumeration with a composite HID+CDC descriptor before accepting a lot. MOQ is one tray (250 pcs) or 100 pcs loose for prototypes; Shenzhen stock commonly holds several thousand pieces with 1-2 day dispatch.
Key Features
- Native USB 2.0 full-speed device with six programmable endpoints - no bridge chip
- 32 KB Flash, 2.5 KB SRAM, 1 KB EEPROM and 26 I/O in a 44-lead TQFP
- 12-channel 10-bit ADC with differential channels and programmable gain
- High-speed timer with 64 MHz PLL for high-resolution PWM plus JTAG debug
- The proven core of Arduino Leonardo, Arduino Micro, Pro Micro and QMK keyboards
Typical Applications
- Custom mechanical keyboards and HID game controllers (QMK/VIA firmware)
- USB-to-serial, USB MIDI and composite HID+CDC dongles
- Arduino Leonardo/Micro compatible boards and shields
- Data-logging and test fixtures that present themselves as a USB drive or CDC port
- Small motor and LED controllers needing high-resolution PWM from a PLL timer
Specifications
- Core
- AVR 8-bit RISC
- Max Clock
- 16 MHz
- Flash
- 32 KB
- SRAM
- 2.5 KB
- I/O Lines
- 26
- Supply Voltage
- 2.7 to 5.5 V
- USB
- 2.0 Full-Speed Device, 6 Endpoints
- ADC
- 12-channel, 10-bit
- Pins
- 44
- RoHS
- Compliant
Procurement Tips
If your product ships with a USB cable and HID firmware, buy genuine ATmega32U4 with lot traceability and pre-test enumeration - a remarked 16U4 passes ISP signature checks only if remarked correctly, but fails the moment firmware exceeds 16 KB, which is a field return rather than an incoming-quality catch.
Frequently Asked Questions
Why does the ATmega32U4 not need a USB-to-UART chip like the ATmega328P?
Because the USB device controller is on the die. The 328P has no USB peripheral at all, so boards such as the Uno add an ATmega16U2 or CH340 as a bridge. On the 32U4 the D+ and D- pins connect straight to the USB PHY, and firmware (LUFA, Arduino core or QMK) handles enumeration, descriptors and endpoints directly.
Can the ATmega32U4 act as a USB host?
No. It is a device-only controller (full-speed 12 Mbps and low-speed 1.5 Mbps). For host mode you need the AT90USB646/1286 family or a 32-bit part such as the STM32F4 with OTG. If your product must read from a USB flash drive or a HID keyboard, plan around a host-capable MCU.
Will it work at 3.3 V and 16 MHz?
No. Per Microchip the maximum frequency at 2.7 V is 8 MHz and 16 MHz requires 4.5 V minimum. The popular 3.3 V Pro Micro boards therefore run 8 MHz, and USB full-speed needs the 16 MHz clock path - which is why 3.3 V/8 MHz variants require the corresponding fuse and clock configuration and sometimes a different USB PLL setup. Use 5 V with a 16 MHz crystal for full-speed USB.
What is the difference between the -AU (TQFP) and -MU (QFN) versions?
Same die and electrical specifications. -AU is the 44-lead TQFP at 10 x 10 mm, hand-solderable and easy to inspect; -MU is the 44-pad QFN at 7 x 7 mm for compact boards, requiring reflow and X-ray-capable inspection. Choose TQFP for prototyping and repairable products, QFN for volume and space-constrained layouts.
How do I spot a counterfeit or remarked ATmega32U4?
Read the signature bytes over ISP or JTAG: a genuine ATmega32U4 returns 1E 95 87, while an ATmega16U4 returns 1E 94 88 and will fail once your firmware exceeds 16 KB. Then exercise all six USB endpoints with a composite descriptor and verify bulk transfer integrity - clones often have reduced endpoint RAM. Physically check laser etching, lead finish and date-code consistency across the reel.
What is the MOQ and lead time for the ATMEGA32U4-AU?
One tray (250 pcs) for prototypes or 100 pcs loose; production runs are typically 1,000-5,000 pcs. Microchip authorised channel lead time has ranged 12-26 weeks during shortages. Our Shenzhen stock usually covers 3,000-10,000 pcs with 1-2 business day dispatch and can ship a C-of-C plus lot traceability.
Alternatives & Equivalents
View full cross-reference table →Need ATMEGA32U4-AU pricing and availability?
Submit an RFQ — we reply within 24 hours with stock, pricing, lead time and packaging options.
Request a Quote →